Persons with NIDDM especially women have abnormal oxygen consumption (VO2) responses to exercise even in the absence of cardiovascular disease. We hypothesize that in persons with niddm compared to nondiabetic persons, decreased maximal and dynasmic cardiac output responses are associated with impaired (VO2) responses. We also hypothesize that the impaired exercise performance observed in niddm is associated with decreased levels of habitual physical activity compared to control values.